Lowering Feed Costs

Recent corn price increases have left animal nutrition researchers
looking for alternatives that maintain milk production

When corn prices rise, you can rein in feed costs without sacrificing
milk production. The key to successfully replacing starch from high-priced
corn is using non-forage fibre, research has shown.

Recent corn price increases have resulted from competing uses and
growing global demand, leaving animal nutrition researchers to look
at ways to lower costs. In dairy rations, starch is a major energy
component, and corn is the predominant starch source in much of
Canada and the U.S. Other grains, such as barley, may be a more
common starch source in areas where corn is not as readily available.

Starch is used to formulate today's energy-dense rations needed
by high-producing cows. Starch fermenting in the cows' rumens produces
volatile fatty acids and contributes to the growth of rumen microbes
to generate microbial protein. When digested by cows, microbial
protein contributes to milk production and maintaining energy balance
and body condition.

Too much starch fermentation can lead to health issues such as
ruminal acidosis. Digestion rates depend on starch concentration,
how much of it is exposed -whole corn is less exposed than cracked
corn, which is less than ground corn-and the extent the starch is
bound to the kernel's other components.

Current milking ration starch content recommendations vary. Rations
are typically in the 23 to 30 per cent starch range, with an optimum
suggested at 24 to 26 per cent.

During the last 10 years or so, a lot of interest has developed
in partially replacing corn in rations with alternative feed ingredients.
These are primarily from non-forage fibre byproduct feeds such as
dried distillers grains, beet pulp, citrus pulp and soybean hulls.
They have much lower starch concentrations than corn.

South Dakota State University researchers, known for their expertise
in feeding dried corn distillers grains to dairy cattle, have reported
on an experiment investigating the effect of reducing starch in
the diet to 20 per cent from 29 per cent. The four diets used in
the experiment are shown in the table on page xx.

The amount of distillers grains in the four diets was zero, seven
per cent, 14 per cent and 21 per cent. The table shows other ingredient
changes the researchers made to try to keep composition of the diets
as consistent as possible.

As they increased the amount of distillers grains, however, total
fat content rose to 5.48 per cent in the diet with 21 per cent distillers
grains from 4.35 per cent in the diet with no distillers grains.
This resulted from the distillers grains' fat content.

After six weeks of being fed different diets, cows had no statistical
difference in milk production or fat and protein in terms of both
yield and percentage content in milk. Cows did reduce their dry
matter intake (DMI) as the amount of starch in their diet decreased
and the amount of soybean hulls and distillers grains increased.
DMI declined to 22.9 kilograms per day on the 20 per cent starch
diet from 25.6 kg per day on the 29 per cent starch diet.

The researchers calculated feed efficiency based on energy-corrected
milk per DMI. It increased to 1.61 from 1.47 as the starch level
decreased and total neutral detergent fibre (NDF) increased.

Decreased DMI can be linked to increased NDF above 32 per cent
dry matter, although this relationship is far weaker with non-forage
NDF than with forage NDF.

This study's results tend to agree with other reports that it is
possible to replace starch in diets with non-forage fibre sources
from distillers grains and soybean hulls. Several other studies
agree with this one that a drop in DMI as a result of distillers
grains inclusion need not affect milk yield. One Alberta study found
a 10 percentage point drop in starch concentration did not affect
milk yield, possibly due to the increased fat content and highly
digestible NDF in distillers grains.

The economics of lower starch diets pay off when corn prices are
high. When they lowered starch to 20 from 29 per cent, the South
Dakota researchers calculated feed costs decreased to $3.49 from
$4.91 per cow per day-a savings of $1.42.

These savings highlight the need for more low-starch diet studies,
particularly below 21 per cent starch and for longer terms. Most
studies like this one have not lasted for a full lactation, but
many U.S. herds are achieving good milk production with starch levels
as low as 15 to 19 per cent.

If you are thinking of adopting a low-starch ration, watch for
decreased milk production, decreased body condition, reduced milk
protein and increased milk urea nitrogen (MUN). When using distillers
grains, regularly monitor the product's nutrient variability, including
sulphur levels in the whole ration at high feeding rates. Starch
digestibility of all ingredients plays a key role in successfully
implementing a lower starch ration.

Anne Laarman is a graduate student, department of animal and poultry
science, University of Guelph, Brian McBride is a professor, department
of animal and poultry science, University of Guelph, and Tom Wright,
is OMAFRA's dairy cattle nutritionist.

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